Crank assembly for human powered vehicle

ABSTRACT

A crank assembly comprises a crank arm, a front sprocket unit, and at least one chain-drop control protrusion. The at least one chain-drop control protrusion is configured to inhibit a drive chain from getting into a space provided radially inwardly from the at least one control protrusion and between the crank arm and the front sprocket unit in the axial direction. The at least one chain-drop control protrusion is configured to be provided to at least one of an axially inwardly facing crank-surface of the crank arm and an axially outwardly facing sprocket-surface of the front sprocket unit. The at least one chain-drop control protrusion has a through bore.

BACKGROUND Technical Field

The present invention relates to a crank assembly for a human poweredvehicle.

Background Information

A human powered vehicle includes a crank unit. The crank unit includesan arm and a sprocket. A pedal is attached to the arm. The sprocket isrotatable along with the arm. A chain is engaged with sprocket teeth ofthe sprocket. The chain may drop off from the sprocket teeth toward thearm. It is preferable to restrict the chain from getting into a spaceprovided between the sprocket and the arm when the chain drops off fromthe sprocket teeth.

SUMMARY

In accordance with a first aspect of the present invention, a crankassembly for a human-powered vehicle comprises a crank arm, a frontsprocket unit, and at least one chain-drop control protrusion. The crankarm has an axially outwardly facing crank-surface and an axiallyinwardly facing crank-surface provided on a reverse side of the axiallyoutwardly facing crank-surface in an axial direction with respect to arotational center axis of the crank assembly. The axially inwardlyfacing crank-surface is configured to face toward an axial center planeof the human powered vehicle in the axial direction in a mounted statewhere the crank assembly is mounted to the human powered vehicle. Thefront sprocket unit has an axially outwardly facing sprocket-surface andan axially inwardly facing sprocket-surface provided on a reverse sideof the axially outwardly facing sprocket-surface in the axial direction.The axially inwardly facing sprocket-surface is configured to facetoward the axial center plane of the human powered vehicle in the axialdirection in the mounted state. The front sprocket unit includes asprocket body and a plurality of sprocket teeth extending radiallyoutwardly from the sprocket body in a radial direction with respect tothe rotational center axis. The at least one chain-drop controlprotrusion is configured to inhibit a drive chain from getting into aspace provided radially inwardly from the at least one controlprotrusion and between the crank arm and the front sprocket unit in theaxial direction. The at least one chain-drop control protrusion isconfigured to be provided to at least one of the axially inwardly facingcrank-surface of the crank arm and the axially outwardly facingsprocket-surface of the front sprocket unit. The at least one chain-dropcontrol protrusion has a through bore.

With the crank assembly according to the first aspect, the through boresaves weight of the at least one chain-drop control protrusion. Thus,the at least one chain-drop control protrusion can restrict the drivechain from getting into the space provided between the front sprocketunit and the crank arm when the drive chain drops off from the pluralityof sprocket teeth of the front sprocket unit while saving weight of thecrank assembly.

In accordance with a second aspect of the present invention, the crankassembly according to the first aspect is configured so that the atleast one chain-drop control protrusion has a free end and an attachmentend configured to be coupled to the at least one of the axially inwardlyfacing crank-surface of the crank arm and the axially outwardly facingsprocket-surface of the front sprocket unit. The through bore has a borecenter-axis extending from one of the free end and the attachment end tothe other of the free end and the attachment end.

With the crank assembly according to the second aspect, the at least onechain-drop control protrusion can restrict the drive chain from gettinginto the space provided between the front sprocket unit and the crankarm when the drive chain drops off from the plurality of sprocket teethof the front sprocket unit while reliably saving weight of the crankassembly.

In accordance with a third aspect of the present invention, the crankassembly according to the second aspect is configured so that the atleast one chain-drop control protrusion has a chain-drop control sectionand an attachment section adjacent to the chain-drop control section ina bore axial direction with respect to the bore center-axis. Thechain-drop control section includes the free end. The attachment sectionincludes the attachment end.

With the crank assembly according to the third aspect, the chain-dropcontrol section can reliably restrict the drive chain from getting intothe space provided between the front sprocket unit and the crank armwhen the drive chain drops off from the plurality of sprocket teeth ofthe front sprocket unit while saving weight of the crank assembly.

In accordance with a fourth aspect of the present invention, the crankassembly according to the third aspect is configured so that thechain-drop control section has a first maximum diameter with respect tothe bore center-axis. The attachment section has a second maximumdiameter with respect to the bore center-axis. The first maximumdiameter is larger than the second maximum diameter.

With the crank assembly according to the fourth aspect, the secondmaximum diameter can reduce a size of an attachment hole of the frontsprocket unit to which the attachment section is attached. Thus, it ispossible to ensure rigidity of at least one of the front sprocket unitand the crank arm.

In accordance with a fifth aspect of the present invention, the crankassembly according to the third or fourth aspect is configured so thatthe chain-drop control section has a first axial length with respect tothe bore center-axis. The attachment section has a second axial lengthwith respect to the bore center-axis. The first axial length is largerthan the second axial length.

With the crank assembly according to the fifth aspect, it is possible toreliably save weight of the at least one chain-drop control protrusion.

In accordance with a sixth aspect of the present invention, the crankassembly according to any one of the third to fifth aspects isconfigured so that the chain-drop control section has a radiallyoutermost surface with respect to the bore center-axis and a chamferedportion. The free end has an axial free-end surface with respect to thebore center-axis. The chamfered portion is provided between the radiallyoutermost surface and the axial free-end surface.

With the crank assembly according to the sixth aspect, the chamferedportion enables the chain-drop control section to be arranged closer toone of the front sprocket unit and the crank arm while the at least onechain-drop control protrusion restricts the drive chain from gettinginto the space provided between the front sprocket unit and the crankarm when the drive chain drops off from the plurality of sprocket teethof the front sprocket unit while reliably saving weight of the crankassembly.

In accordance with a seventh aspect of the present invention, the crankassembly according to the sixth aspect is configured so that thechamfered portion has a curvature.

With the crank assembly according to the seventh aspect, the chamferedportion reliably enables the chain-drop control section to be arrangedcloser to one of the front sprocket unit and the crank arm while the atleast one chain-drop control protrusion restricts the drive chain fromgetting into the space provided between the front sprocket unit and thecrank arm when the drive chain drops off from the plurality of sprocketteeth of the front sprocket unit while reliably saving weight of thecrank assembly.

In accordance with an eighth aspect of the present invention, the crankassembly according to any one of the third to seventh aspects isconfigured so that the through bore has a threaded portion provided atleast in the chain-drop control section of the at least one chain-dropcontrol protrusion.

With the crank assembly according to the eighth aspect, the threadedportion enables another member to be attached to the at least onechain-drop control protrusion.

In accordance with a ninth aspect of the present invention, the crankassembly according to the eighth aspect further comprises an additionalchain-drop control protrusion configured to threadedly engage with thethreaded portion of the through bore.

With the crank assembly according to the ninth aspect, it is possible toadapt the at least one chain-drop control protrusion to a variety ofcrank assemblies by attaching or detaching the additional chain-dropcontrol protrusion to or from the at least one chain-drop controlprotrusion.

In accordance with a tenth aspect of the present invention, the crankassembly according to any one of the third to ninth aspects isconfigured so that the through bore has a large diameter bore and asmall diameter bore connected to the large diameter bore. The largediameter bore extends from the free end in a bore axial direction withrespect to the bore center-axis. The small diameter bore extends fromthe attachment end in the bore axial direction.

With the crank assembly according to the tenth aspect, it is possible toattach another member to the at least one chain-drop control protrusionusing at least one of the large diameter bore and the small diameterbore with accuracy.

In accordance with an eleventh aspect of the present invention, thecrank assembly according to the tenth aspect is configured so that thelarge diameter bore and the small diameter bore are connected to eachother at a connecting point. The threaded portion extends from theconnecting point along the bore axial direction in the small diameterbore.

With the crank assembly according to the eleventh aspect, it is possibleto attach another member to the at least one chain-drop controlprotrusion using at least one of the large diameter bore and the smalldiameter bore with higher accuracy.

In accordance with a twelfth aspect of the present invention, the crankassembly according to the eleventh aspect is configured so that theconnecting point is located in the chain-drop control section.

With the crank assembly according to the twelfth aspect, the location ofthe connecting point makes the small diameter bore longer. Thus, it ispossible to reliably attach another member to the at least onechain-drop control protrusion using the small diameter bore with higheraccuracy.

In accordance with a thirteenth aspect of the present invention, thecrank assembly according to any one of the third to twelfth aspects isconfigured so that the attachment section has a non-circularcross-sectional shape.

With the crank assembly according to the thirteenth aspect, thenon-circular cross-sectional shape can restrict the at least onechain-drop control protrusion from rotating relative to at least one ofthe crank arm and the front sprocket unit when another member isattached to the at least one chain-drop control protrusion.

In accordance with a fourteenth aspect of the present invention, thecrank assembly according to any one of the eighth to thirteenth aspectsis configured so that the at least one chain-drop control protrusion hasa chain-drop control section and an attachment section adjacent to thechain-drop control section in a bore axial direction with respect to thebore center-axis. The through bore has a non-threaded portion providedin the attachment section and adjacent to the threaded portion. Thenon-threaded portion has a non-threaded internal diameter that is equalto an internal minor diameter of the threaded portion.

With the crank assembly according to the fourteenth aspect, thenon-threaded portion makes it possible to easily form the threadedportion in the through bore.

In accordance with a fifteenth aspect of the present invention, thecrank assembly according to any one of the first to fourteenth aspectsfurther comprises an electrical component provided to the crank arm at alocation radially inwardly from the at least one chain-drop controlprotrusion.

With the crank assembly according to the fifteenth aspect, the at leastone chain-drop control protrusion can reduce interference between thedrive chain and the electrical component when the drive chain drops offfrom the plurality of sprocket teeth of the front sprocket unit. Thus,it is possible to protect the electrical component from the drive chainwhen the drive chain drops off from the plurality of sprocket teeth ofthe front sprocket unit.

In accordance with a sixteenth aspect of the present invention, thecrank assembly according to the fifteenth aspect is configured so thatthe electrical component includes a force sensor.

With the crank assembly according to the sixteenth aspect, the at leastone chain-drop control protrusion can protect the force sensor from thedrive chain when the drive chain drops off from the plurality ofsprocket teeth of the front sprocket unit.

In accordance with a seventeenth aspect of the present invention, thecrank assembly according to the fifteenth or sixteenth aspect furthercomprises a cover member configured to be attached to the axiallyinwardly facing crank-surface of the crank arm so as to cover theelectrical component in an assembled state of the crank assembly.

With the crank assembly according to the seventeenth aspect, the atleast one chain-drop control protrusion can protect the cover memberfrom the drive chain when the drive chain drops off from the pluralityof sprocket teeth of the front sprocket unit. Furthermore, the covermember can reliably protect the electrical component from the drivechain when the drive chain drops off from the plurality of sprocketteeth of the front sprocket unit.

In accordance with an eighteenth aspect of the present invention, thecrank assembly according to the seventeenth aspect is configured so thatthe cover member is made of a non-metallic material.

With the crank assembly according to the eighteenth aspect, the at leastone chain-drop control protrusion can protect the cover member made ofthe non-metallic material from the drive chain when the drive chaindrops off from the plurality of sprocket teeth of the front sprocketunit. Furthermore, the cover member can reliably protect the electricalcomponent from the drive chain when the drive chain drops off from theplurality of sprocket teeth of the front sprocket unit while savingweight of the crank assembly.

In accordance with a nineteenth aspect of the present invention, thecrank assembly according to any one of the first to eighteenth aspectsis configured so that the at least one chain-drop control protrusionincludes a plurality of chain-drop control protrusions spaced apart fromeach other in a circumferential direction with respect to the rotationalcenter axis.

With the crank assembly according to the nineteenth aspect, theplurality of chain-drop control protrusions can reliably restrict thedrive chain from getting into the space provided between the frontsprocket unit and the crank arm when the drive chain drops off from theplurality of sprocket teeth of the front sprocket unit.

In accordance with a twentieth aspect of the present invention, thecrank assembly according to any one of the first to nineteenth aspectsis configured so that the at least one chain-drop control protrusion isdisposed radially inwardly from the plurality of sprocket teeth.

With the crank assembly according to the twentieth aspect, the at leastone chain-drop control protrusion can reliably restrict the drive chainfrom getting into the space provided between the front sprocket unit andthe crank aim when the drive chain drops off from the plurality ofsprocket teeth of the front sprocket unit.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1 is a perspective view of a crank assembly in accordance with afirst embodiment.

FIG. 2 is a side-elevational view of the crank assembly illustrated inFIG. 1 , with one of crank arms omitted.

FIG. 3 is a cross-sectional view of the crank assembly taken along lineof FIG. 2 .

FIG. 4 is another side-elevational view of the crank assemblyillustrated in FIG. 1 .

FIG. 5 is a cross-sectional view of the crank assembly taken along lineV-V of FIG. 2 .

FIG. 6 is a partial perspective view of the crank assembly illustratedin FIG. 1 .

FIG. 7 is a partial top view of the crank assembly illustrated in FIG. 1.

FIG. 8 is a cross-sectional view of the crank assembly taken along lineVIII-VIII of FIG. 7 .

FIG. 9 is a partial side-elevational view of the crank assemblyillustrated in FIG. 1 .

FIG. 10 is a partial cross-sectional view of the crank assembly takenalong line X-X of FIG. 9 .

FIG. 11 is a partial cross-sectional view of the crank assembly takenalong line XI-XI of FIG. 9 .

FIG. 12 is a partial cross-sectional view of the crank assembly takenalong line XII-XII of FIG. 9 .

FIG. 13 is an enlarged partial cross-sectional view of the crankassembly illustrated in FIG. 12 .

FIG. 14 is a partial cross-sectional view of the crank assembly takenalong line XIV-XIV of FIG. 7 .

FIG. 15 is a partial cross-sectional view of the crank assembly inaccordance with a modification.

FIG. 16 is a partial cross-sectional view of the crank assembly takenalong line XVI-XVI of FIG. 7 .

FIG. 17 is a partial cross-sectional view of the crank assembly takenalong line XVII-XVII of FIG. 7 .

FIG. 18 is a perspective view of a crank assembly in accordance with asecond embodiment.

FIG. 19 is a partial perspective view of the crank assembly illustratedin FIG. 18 .

FIG. 20 is a partial cross-sectional view of the crank assembly takenalong line XX-XX of FIG. 18 .

FIG. 21 is another perspective view of a crank assembly illustrated inFIG. 18 .

FIG. 22 is an enlarged partial cross-sectional view of the crankassembly illustrated in FIG. 20 .

FIG. 23 is a perspective view of a crank assembly in accordance with athird embodiment.

FIG. 24 is a partial perspective view of the crank assembly illustratedin FIG. 23 .

FIG. 25 is a partial cross-sectional view of the crank assembly takenalong line XXV-XXV of FIG. 23 .

FIG. 26 is an enlarged partial cross-sectional view of the crankassembly illustrated in FIG. 25 .

FIG. 27 is a side-elevational view of the crank assembly illustrated inFIG. 23 .

FIG. 28 is a partial side-elevational view of the crank assemblyillustrated in FIG. 23 .

FIG. 29 is a partial cross-sectional view of the crank assembly takenalong line XXIX-XXIX of FIG. 28 .

FIG. 30 is a partial top view of a crank assembly in accordance with amodification.

FIG. 31 is a partial top view of a crank assembly in accordance withanother modification.

FIG. 32 is a partial rear view of a crank assembly in accordance withanother modification.

FIG. 33 is a partial rear view of a crank assembly in accordance withanother modification.

DESCRIPTION OF THE EMBODIMENTS

The embodiment(s) will now be described with reference to theaccompanying drawings, wherein like reference numerals designatecorresponding or identical elements throughout the various drawings.

First Embodiment

As seen in FIG. 1 , a crank assembly 10 for a human powered vehicle 2 isrotatable relative to a vehicle body 2A about a rotational center axisA1. The crank assembly 10 is configured to be rotated relative to thevehicle body 2A about the rotational center axis A1 in a rotationaldriving direction D1 during pedaling.

In the present application, a human powered vehicle is a vehicle totravel with a motive power including at least a human power of a userwho rides the human powered vehicle (i.e., rider). The human poweredvehicle includes a various kind of bicycles such as a mountain bike, aroad bike, a city bike, a cargo bike, a hand bike, and a recumbent bike.Furthermore, the human powered vehicle includes an electric bike(E-bike). The electric bike includes an electrically assisted bicycleconfigured to assist propulsion of a vehicle with an electric motor.However, a total number of wheels of the human powered vehicle is notlimited to two. For example, the human powered vehicle includes avehicle having one wheel or three or more wheels. Especially, the humanpowered vehicle does not include a vehicle that uses only aninternal-combustion engine as motive power. Generally, a light roadvehicle, which includes a vehicle that does not require a driver'slicense for a public road, is assumed as the human powered vehicle.

In the present application, the following directional terms “front,”“rear,” “forward,” “rearward,” “left,” “right,” “transverse,” “upward”and “downward” as well as any other similar directional terms refer tothose directions which are determined on the basis of a user (e.g., arider) who is in the user's standard position (e.g., on a saddle or aseat) in the human powered vehicle 2 with facing a handlebar or asteering. Accordingly, these terms, as utilized to describe the crankassembly 10 or other components, should be interpreted relative to thehuman powered vehicle 2 equipped with the crank assembly 10 or othercomponents as used in an upright riding position on a horizontalsurface.

As seen in FIG. 1 , the crank assembly 10 for the human powered vehicle2 comprises a crank arm 12 and a front sprocket unit 14. The crankassembly 10 comprises a crank axle 16. The crank axle 16 extends alongthe rotational center axis A1. The crank axle 16 is configured to berotatably supported by the vehicle body 2A about the rotational centeraxis A1. The crank arm 12 is secured to the crank axle 16 to rotatealong with the crank axle 16 relative to the vehicle body 2A about therotational center axis A1. The crank assembly 10 includes an additionalcrank arm secured to the crank axle 16. In the present embodiment, thecrank arm 12 is a right crank arm. The additional crank arm is a leftcrank arm. However, the structure of the crank arm 12 can be applied toa left crank arm if needed and/or desired.

The front sprocket unit 14 is configured to be engaged with a drivechain 4. The front sprocket unit 14 is secured to at least one of thecrank arm 12 and the crank axle 16. In the first embodiment, the frontsprocket unit 14 is directly secured to the crank arm 12 with aplurality of fasteners 17. However, the front sprocket unit 14 can bedirectly secured to the crank axle 16 or both the crank arm 12 and thecrank axle 16 if needed and/or desired.

As seen in FIG. 2 , the front sprocket unit 14 includes a first frontsprocket 18 and a second front sprocket 20. The first front sprocket 18and the second front sprocket 20 are secured to the crank arm 12 withthe plurality of fasteners 17.

The first front sprocket 18 includes a sprocket body 18A and a pluralityof sprocket teeth 18B. Namely, the front sprocket unit 14 includes thesprocket body 18A and the plurality of sprocket teeth 18B. The sprocketbody 18A of the first front sprocket 18 is secured to the crank arm 12with the plurality of fasteners 17. The plurality of sprocket teeth 18Bextends radially outwardly from the sprocket body 18A in the radialdirection with respect to the rotational center axis A1.

The first front sprocket 18 can also be referred to as a front sprocket18. The sprocket body 18A can also be referred to as a first sprocketbody 18A. The sprocket tooth can also be referred to as a first sprockettooth.

The second front sprocket 20 includes a second sprocket body 20A and aplurality of second sprocket teeth 20B. The second sprocket body 20A ofthe second front sprocket 20 is secured to the crank arm 12 with theplurality of fasteners 17. The plurality of second sprocket teeth 20Bextends radially outwardly from the second sprocket body 20A in theradial direction with respect to the rotational center axis A1.

The first front sprocket 18 has a first sprocket outer diameter DM11.The second front sprocket 20 has a second sprocket outer diameter DM12.The first sprocket outer diameter DM11 is larger than the secondsprocket outer diameter DM12. However, the first sprocket outer diameterDM11 can be smaller than the second sprocket outer diameter DM12 ifneeded and/or desired. The second front sprocket 20 can be omitted fromthe front sprocket unit 14 if needed and/or desired.

As seen in FIG. 2 , the crank arm 12 includes a plurality of couplingparts 22. As seen in FIG. 3 , the plurality of coupling parts 22 isprovided between the first front sprocket 18 and the second frontsprocket 20 in an axial direction D2 with respect to the rotationalcenter axis A1 of the crank assembly 10.

As seen in FIG. 4 , the front sprocket unit 14 includes a plurality ofreceiving members 24. As seen in FIG. 3 , the receiving member 24includes a threaded hole 24A. The fastener 17 includes an externalthread 17A. The external thread 17A is engaged with the threaded hole24A.

As seen in FIG. 5 , the crank arm 12 has an axially outwardly facingcrank-surface 12A and an axially inwardly facing crank-surface 12B. Theaxially inwardly facing crank-surface 12B is provided on a reverse sideof the axially outwardly facing crank-surface in the axial direction D2with respect to the rotational center axis A1 of the crank assembly 10.

The axially inwardly facing crank-surface 12B is configured to facetoward an axial center plane CP of the human powered vehicle 2 in theaxial direction D2 in a mounted state where the crank assembly 10 ismounted to the human powered vehicle 2. The axial center plane CP isperpendicular to the rotational center axis A1. For example, the axialcenter plane CP is defined to bisect an axial width of the vehicle body2A in the axial direction D2.

The front sprocket unit 14 has an axially outwardly facingsprocket-surface 14A and an axially inwardly facing sprocket-surface14B. The axially inwardly facing sprocket-surface 14B is provided on areverse side of the axially outwardly facing sprocket-surface 14A in theaxial direction D2. The axially inwardly facing sprocket-surface 14B isconfigured to face toward the axial center plane CP of the human poweredvehicle 2 in the axial direction D2 in the mounted state.

The axially inwardly facing crank-surface 12B is configured to facetoward the front sprocket unit 14 in the axial direction D2. The axiallyinwardly facing crank-surface 12B is configured to face toward theaxially outwardly facing sprocket-surface 14A of the front sprocket unit14 in the axial direction D2.

The axially inwardly facing crank-surface 12B is spaced apart from thefront sprocket unit 14 in the axial direction D2. The axially inwardlyfacing crank-surface 12B is spaced apart from the axially outwardlyfacing sprocket-surface 14A of the front sprocket unit 14 in the axialdirection D2.

As seen in FIG. 6 , the crank assembly 10 for the human powered vehicle2 comprises at least one chain-drop control protrusion 30. In thepresent embodiment, the at least one chain-drop control protrusion 30includes a plurality of chain-drop control protrusions 30. Namely, thecrank assembly 10 for the human powered vehicle 2 comprises theplurality of chain-drop control protrusions 30.

A total number of the plurality of chain-drop control protrusions 30 isequal to or larger than three. In the present embodiment, the totalnumber of the plurality of chain-drop control protrusions 30 is equal tothree. However, the total number of the plurality of chain-drop controlprotrusions 30 can be larger than or equal to two if needed and/ordesired.

As seen in FIG. 5 , the at least one chain-drop control protrusion 30 isconfigured to inhibit the drive chain 4 from getting into a space SPradially inwardly from the at least one control protrusion and betweenthe crank arm 12 and the front sprocket unit 14 in the axial directionD2. The plurality of chain-drop control protrusions 30 is configured toinhibit the drive chain 4 from getting into the space SP providedradially inwardly from the plurality of chain-drop control protrusions30 and between the crank arm 12 and the front sprocket unit 14 in theaxial direction D2.

The at least one chain-drop control protrusion 30 is configured to beprovided to at least one of the crank arm 12 and the front sprocket unit14. The plurality of chain-drop control protrusions 30 is configured tobe provided to at least one of the crank arm 12 and the front sprocketunit 14.

The at least one chain-drop control protrusion 30 is configured to beprovided to at least one of the axially inwardly facing crank-surface12B of the crank arm 12 and the axially outwardly facingsprocket-surface 14A of the front sprocket unit 14. The plurality ofchain-drop control protrusions 30 is configured to be provided to atleast one of the axially inwardly facing crank-surface 12B of the crankarm 12 and the axially outwardly facing sprocket-surface 14A of thefront sprocket unit 14.

In the present embodiment, the plurality of chain-drop controlprotrusions 30 is configured to be provided to the front sprocket unit14 among the crank arm 12 and the front sprocket unit 14. The pluralityof chain-drop control protrusions 30 is configured to be provided to theaxially outwardly facing sprocket-surface 14A among the axially inwardlyfacing crank-surface 12B and the axially outwardly facingsprocket-surface 14A. However, the plurality of chain-drop controlprotrusions 30 can be configured to be provided to only the crank arm 12or both of the crank arm 12 and the front sprocket unit 14 if neededand/or desired. The plurality of chain-drop control protrusions 30 canbe configured to be provided to the axially inwardly facingcrank-surface 12B of the crank arm 12 or both of the axially inwardlyfacing crank-surface 12B of the crank arm 12 and the axially outwardlyfacing sprocket-surface 14A of the front sprocket unit 14 if neededand/or desired.

As seen in FIGS. 7 and 8 , the plurality of chain-drop controlprotrusions 30 is spaced apart from each other in a circumferentialdirection D3 with respect to the rotational center axis A1. In thepresent embodiment, the plurality of chain-drop control protrusions 30is directly coupled to the first front sprocket 18. The plurality ofchain-drop control protrusions 30 is directly coupled to the sprocketbody 18A of the first front sprocket 18. However, at least onechain-drop control protrusion of the plurality of chain-drop controlprotrusions 30 can be directly coupled to a cover attached to at leastone of the first front sprocket 18 and the second front sprocket 20 ifneeded and/or desired.

As seen in FIG. 8 , the at least one chain-drop control protrusion isdisposed radially inwardly from the plurality of sprocket teeth 18B. Theplurality of chain-drop control protrusions 30 is at least partiallydisposed radially inwardly from the sprocket teeth 18B. The plurality ofchain-drop control protrusions 30 is entirely disposed radially inwardlyfrom the sprocket teeth 18B. However, the plurality of chain-dropcontrol protrusions 30 can be partially disposed radially inwardly fromthe sprocket teeth 18B if needed and/or desired. The plurality ofchain-drop control protrusions 30 can be at least partially disposedradially outwardly from the sprocket teeth 18B if needed and/or desired.

As seen in FIG. 9 , the plurality of chain-drop control protrusions 30overlaps with the crank arm 12 when viewed from the axial direction D2.However, at least one chain-drip control protrusion of the plurality ofchain-drop control protrusions 30 can be provided not to overlap withthe crank arm 12 when viewed from the axial direction D2 if neededand/or desired.

As seen in FIGS. 10 to 12 , the at least one chain-drop controlprotrusion 30 has a through bore 32. At least one chain-drop controlprotrusion of the plurality of chain-drop control protrusions 30 has thethrough bore 32. In the present embodiment, each chain-drop controlprotrusion of the plurality of chain-drop control protrusions 30 has thethrough bore 32. However, the through bore 32 can be omitted from atleast one chain-drop control protrusion of the plurality of chain-dropcontrol protrusions 30 if needed and/or desired.

The at least one chain-drop control protrusion 30 has a free end 33 andan attachment end 34. In the present embodiment, each chain-drop controlprotrusion of the plurality of chain-drop control protrusions 30 has thefree end 33 and the attachment end 34. The through bore 32 has a borecenter-axis A2. The bore center-axis A2 extends from one of the free end33 and the attachment end 34 to the other of the free end 33 and theattachment end 34. The attachment end 34 is configured to be coupled tothe at least one of the axially inwardly facing crank-surface 12B of thecrank arm 12 and the axially outwardly facing sprocket-surface 14A ofthe front sprocket unit 14. The through bore 32 can be formed so thatthe through bore 32 extends to intersect with a direction parallel tothe bore center axis A2 illustrated in FIGS. 10 to 12 .

In the present embodiment, the attachment end 34 is configured to becoupled to the axially outwardly facing sprocket-surface 14A of thefront sprocket unit 14 among the axially inwardly facing crank-surface12B and the axially outwardly facing sprocket-surface 14A. However, theattachment end 34 can be configured to be coupled to only the axiallyinwardly facing crank-surface 12B of the crank arm 12 or both of theaxially inwardly facing crank-surface 12B of the crank arm 12 and theaxially outwardly facing sprocket-surface 14A of the front sprocket unit14 if needed and/or desired.

The at least one chain-drop control protrusion 30 has a chain-dropcontrol section 36 and an attachment section 38. In the presentembodiment, each chain-drop control protrusion of the plurality ofchain-drop control protrusions 30 has the chain-drop control section 36and the attachment section 38. The attachment section 38 is adjacent tothe chain-drop control section 36 in a bore axial direction D4 withrespect to the bore center-axis A2. The attachment section 38 extendsfrom the chain-drop control section 36 in the bore axial direction D4.The chain-drop control section 36 includes the free end 33. Theattachment section 38 includes the attachment end 34. The chain-dropcontrol section 36 is contactable with the drive chain 4 when the drivechain 4 drops off from the front sprocket unit 14 (e.g., the first frontsprocket 18). The attachment section 38 is secured to the front sprocketunit 14 (e.g., the first front sprocket 18).

In the present embodiment, the chain-drop control section 36 isintegrally provided with the attachment section 38 as a one-pieceunitary member. However, the chain-drop control section 36 can be aseparate member from the attachment section 38 if needed and/or desired.

As seen in FIG. 13 , the front sprocket unit 14 includes an attachmenthole 40. The first front sprocket 18 includes the attachment hole 40.The sprocket body 18A includes the attachment hole 40. The attachmentsection 38 is at least partially provided in the attachment hole 40. Theattachment section 38 extends through the attachment hole 40. Thechain-drop control section 36 is provided outside the attachment hole40. In the present embodiment, the attachment section 38 is partiallyprovided in the attachment hole 40. However, the attachment section 38can be entirely provided in the attachment hole 40 if needed and/ordesired.

The attachment section 38 includes a first attachment section 38A and asecond attachment section 38B. The second attachment section 38Bincludes the attachment end 34. The first attachment section 38A isprovided in the attachment hole 40. The second attachment section 38B isprovided outside the attachment hole 40. The second attachment section38B has an outer diameter larger than an outer diameter of the firstattachment section 38A. For example, the second attachment section 38Bis formed by being swaged. However, the second attachment section 38Bcan be formed by other methods. The second attachment section 38B can beomitted from the attachment section 38 e.g. if the attachment section 38is coupled to the attachment hole 40 by an adhesive agent or in apress-fitting manner.

The chain-drop control section 36 has a first maximum diameter DM21 withrespect to the bore center-axis A2. The attachment section 38 has asecond maximum diameter DM22 with respect to the bore center-axis A2.The second maximum diameter DM22 is defined by the second attachmentsection 38B. In the present embodiment, the first maximum diameter DM21is larger than the second maximum diameter DM22. A ratio of the firstmaximum diameter DM21 to the second maximum diameter DM22 is greaterthan or equal to 1.2. In the present embodiment, the first maximumdiameter DM21 is equal to 4 mm. The second maximum diameter DM22 isequal to 3 mm. The ratio of the first maximum diameter DM21 to thesecond maximum diameter DM22 is equal to 1.33. However, the ratio of thefirst maximum diameter DM21 to the second maximum diameter DM22 is notlimited to the above ratio and range. The first maximum diameter DM21 isnot limited to the above diameter. The second maximum diameter DM22 isnot limited to the above diameter.

The chain-drop control section 36 has a first axial length L1 withrespect to the bore center-axis A2. The attachment section 38 has asecond axial length L2 with respect to the bore center-axis A2. Thefirst axial length L1 is larger than the second axial length L2. A ratioof the first axial length L1 to the second axial length L2 is greaterthan or equal to 1.5. In the present embodiment, the first axial lengthL1 is equal to 3.2 mm. The second axial length L2 is equal to 2 mm. Theratio of the first axial length L1 to the second axial length L2 isequal to 1.6. However, the ratio of the first axial length L1 to thesecond axial length L2 is not limited to the above ratio and range. Thefirst axial length L1 is not limited to the above length. The secondaxial length L2 is not limited to the above length.

As seen in FIG. 13 , the chain-drop control section 36 has a radiallyoutermost surface 36A with respect to the bore center-axis A2. The freeend 33 has an axial free-end surface 33A with respect to the borecenter-axis A2. The chain-drop control section 36 has a chamferedportion 36B. The chamfered portion 36B is provided between the radiallyoutermost surface 36A and the axial free-end surface 33A.

The chamfered portion 36B has a curvature. The chamfered portion 36Bincludes a curved surface. The curved surface includes a curved convexsurface. The curved surface has the curvature. However, the shape of thechamfered portion 36B is not limited to the illustrated embodiment. Thechamfered portion 36B can include surfaces (e.g., a flat surface) otherthan the curved surface having the curvature if needed and/or desired.

The through bore 32 has a threaded portion 32A. The threaded portion 32Ais provided at least in the chain-drop control section 36 of the atleast one chain-drop control protrusion 30. The threaded portion 32Aincludes an internal thread. In the present embodiment, the threadedportion 32A is entirely provided in the chain-drop control section 36.However, the threaded portion 32A can be partially provided in thechain-drop control section 36 if needed and/or desired.

As seen in FIG. 13 , the through bore 32 has a large diameter bore 32Land a small diameter bore 32S connected to the large diameter bore 32L.The large diameter bore 32L extends from the free end 33 in the boreaxial direction D4 with respect to the bore center-axis A2. The smalldiameter bore 32S extends from the attachment end 34 in the bore axialdirection D4. The large diameter bore 32L has a large diameter DM31. Thesmall diameter bore 32S has a small diameter DM32. The small diameterDM32 of the small diameter bore 32S is smaller than the large diameterDM31 of the large diameter bore 32L. A ratio of the large diameter DM31to the small diameter DM32 is greater than or equal to 1.3.

In the present embodiment, the large diameter DM31 is equal to 2.1 mm.The small diameter DM32 is equal to 1.6 mm. The ratio of the largediameter DM31 to the small diameter DM32 is equal to 1.31. However, theratio of the large diameter DM31 to the small diameter DM32 is notlimited to the above ratio and range. The large diameter DM31 is notlimited to the above length. The small diameter DM32 is not limited tothe above length.

The large diameter bore 32L and the small diameter bore 32S areconnected to each other at a connecting point P1. The threaded portion32A extends from the connecting point P1 along the bore axial directionD4 in the small diameter bore 32S. The connecting point P1 is located inthe chain-drop control section 36. However, the connecting point P1 canbe located in the attachment section 38 if needed and/or desired.

The through bore 32 has a non-threaded portion 32B provided in theattachment section 38. The non-threaded portion 32B is adjacent to thethreaded portion 32A. The non-threaded portion 32B has a non-threadedinternal diameter DM41 that is equal to an internal minor diameter DM42of the threaded portion 32A. The non-threaded internal diameter DM41 andthe internal minor diameter DM42 are equal to the small diameter DM32 ofthe small diameter bore 32S. However, at least one of the non-threadedinternal diameter DM41 and the internal minor diameter DM42 can bedifferent from the small diameter DM32 of the small diameter bore 32S ifneeded and/or desired. The non-threaded internal diameter DM41 can bedifferent from the internal minor diameter DM42 if needed and/ordesired.

As seen in FIG. 13 , the crank assembly 10 further comprises anadditional chain-drop control protrusion 50. The additional chain-dropcontrol protrusion 50 is configured to threadedly engage with thethreaded portion 32A of the through bore 32. The additional chain-dropcontrol protrusion 50 includes a head 52 and a rod 54. The head 52 isprovided at an end of the rod 54. The rod 54 includes an additionalthreaded portion 54A. The additional threaded portion 54A is configuredto threadedly engage with the threaded portion 32A of the through bore32. For example, the additional threaded portion 54A includes anexternal thread.

In the present embodiment, the additional chain-drop control protrusion50 is configured to be attached to the chain-drop control protrusion 30with the threaded portion 32A and the additional threaded portion 54A.However, the additional chain-drop control protrusion 50 can beconfigured to be attached to the chain-drop control protrusion 30 withother structures such as an adhesive agent and press-fitting. In suchmodifications, the threaded portion 32A can be omitted from the throughbore 32 if needed and/or desired. The additional threaded portion 54Acan be omitted from the rod 54 of the additional chain-drop controlprotrusion 50 if needed and/or desired.

The head 52 has a radially outermost surface 52A, an axial end surface52B, and a chamfered portion 52C. The chamfered portion 36B is providedbetween the radially outermost surface 52A and the axial end surface52B. However, the chamfered portion 52C can be omitted from the head 52if needed and/or desired.

As seen in FIG. 6 , the additional chain-drop control protrusion 50includes a tool engagement portion 55. The tool engagement portion 55 isprovided to the head 52. The tool engagement portion 55 includes a toolengagement hole 55A. In the present embodiment, the tool engagement hole55A includes a hexagonal hole. Namely, the additional chain-drop controlprotrusion 50 includes a hexagonal socket screw. However, the toolengagement portion 55 can be omitted from the additional chain-dropcontrol protrusion 50 if needed and/or desired. The tool engagementportion 55 can include structures other than the hexagonal hole ifneeded and/or desired.

As seen in FIG. 13 , the head 52 has a first outer diameter DM51. Therod 54 has a second additional outer diameter DM52. For example, thesecond additional outer diameter DM52 is an external major diameter ofthe additional threaded portion 54A. The first outer diameter DM51 ofthe head 52 is larger than the second additional outer diameter DM52 ofthe rod 54. The first outer diameter DM51 of the head 52 is equal to thefirst maximum diameter DM21 of the chain-drop control section 36. Thefirst outer diameter DM51 of the head 52 is larger than the secondmaximum diameter DM22 of the attachment section 38. The secondadditional outer diameter DM52 of the rod 54 is smaller than the firstmaximum diameter DM21 of the chain-drop control section 36 and thesecond maximum diameter DM22 of the attachment section 38.

However, the first outer diameter DM51 of the head 52 can be smallerthan or equal to the second additional outer diameter DM52 of the rod 54if needed and/or desired. The first outer diameter DM51 of the head 52can be different from the first maximum diameter DM21 of the chain-dropcontrol section 36 if needed and/or desired. The first outer diameterDM51 of the head 52 can be different from the first maximum diameterDM21 of the chain-drop control section 36 if needed and/or desired. Thefirst outer diameter DM51 of the head 52 can be smaller or larger thanthe first maximum diameter DM21 of the chain-drop control section 36 ifneeded and/or desired. The first outer diameter DM51 of the head 52 canbe smaller than or equal to the second maximum diameter DM22 of theattachment section 38 if needed and/or desired.

The head 52 has a third axial length L3. The rod 54 has a fourth axiallength L4. The third axial length L3 is defined in the bore axialdirection D4. The fourth axial length L4 is defined in the bore axialdirection D4. In the present embodiment, the fourth axial length L4 islonger than the third axial length L3. The first axial length L1 of thechain-drop control section 36 is longer than the third axial length L3and the fourth axial length L4. The second axial length L2 of theattachment section 38 is shorter than the third axial length L3 and thefourth axial length L4. However, the fourth axial length L4 can beshorter than or equal to the third axial length L3 if needed and/ordesired. The first axial length L1 of the chain-drop control section 36can be shorter than or equal to at least one of the third axial lengthL3 and the fourth axial length L4 if needed and/or desired. The secondaxial length L2 of the attachment section 38 can be longer than or equalto the third axial length L3 and the fourth axial length L4 if neededand/or desired.

As seen in FIGS. 10 to 12 , the first axial length L1 of the chain-dropcontrol section 36 is longer than a minimum distance L5 defined betweenthe additional chain-drop control protrusion 50 and the crank arm 12 inthe bore axial direction D4. A total of the first axial length L1 andthe third axial length L3 is longer than the minimum distance L5.However, the first axial length L1 of the chain-drop control section 36can be shorter than or equal to the minimum distance L5 if needed and/ordesired. The total of the first axial length L1 and the third axiallength L3 can be shorter than or equal to the minimum distance L5 ifneeded and/or desired.

As seen in FIGS. 9 and 14 , the attachment section 38 has a circularcross-sectional shape. As seen in FIG. 9 , the second attachment section38B has a circular cross-sectional shape. As seen in FIG. 14 , the firstattachment section 38A has a circular cross-sectional shape. Theattachment hole 40 has a circular shape. As seen in FIG. 15 , however,the attachment section 38 can have a non-circular cross-sectional shapeif needed and/or desired. At least one of the first attachment section38A and the second attachment section 38B can have shapes other than acircular cross-sectional shape if needed and/or desired. Thenon-circular cross-sectional shape of the first attachment section 38Arestricts the chain-drop control protrusion 30 from rotating relative tothe front sprocket unit 14.

As seen in FIG. 16 the chain-drop control section 36 has a circularcross-sectional shape. However, the chain-drop control section 36 canhave a non-circular cross-sectional shape if needed and/or desired.

As seen in FIG. 17 the additional chain-drop control protrusion 50 has acircular cross-sectional shape. However, the chain-drop control section36 can have a non-circular cross-sectional shape if needed and/ordesired.

Second Embodiment

A crank assembly 210 in accordance with a second embodiment will bedescribed below referring to FIGS. 18 to 20 . The crank assembly 210 hasthe same structure and/or configuration as those of the crank assembly10 except for an electrical component and the additional chain-dropcontrol protrusion 50. Thus, elements having substantially the samefunction as those in the first embodiment will be numbered the same hereand will not be described and/or illustrated again in detail here forthe sake of brevity.

As seen in FIG. 18 , the crank assembly 210 for the human poweredvehicle 2 comprises the crank arm 12 and the front sprocket unit 14. Thecrank assembly 210 comprises the crank axle 16.

As seen in FIG. 19 , the crank assembly 210 for the human poweredvehicle 2 comprises the at least one chain-drop control protrusion 30.The at least one chain-drop control protrusion 30 includes the pluralityof chain-drop control protrusions 30. In the second embodiment, theadditional chain-drop control protrusion 50 is omitted from the crankassembly 210. However, the crank assembly 210 can include the additionalchain-drop control protrusion 50 if needed and/or desired.

As seen in FIG. 20 , the crank assembly 210 further comprises anelectrical component 260. The electrical component 260 is provided tothe crank arm 12 at a location radially inwardly from the plurality ofchain-drop control protrusions 30. In the present embodiment, theelectrical component 260 includes a force sensor 262. The force sensor262 is configured to sense force applied to the crank arm 12. The forcesensor 262 includes a strain gauge attached to the crank arm 12.However, the force sensor 262 can include sensors other than the straingauge if needed and/or desired. The electrical component 260 can includea component other than the force sensor 262 if needed and/or desired.

The crank assembly 210 further comprises a wireless communicator WC andan electric power source PS. The wireless communicator WC iselectrically connected to the electrical component 260. The wirelesscommunicator WC is electrically connected to the force sensor 262. Thewireless communicator WC is configured to wirelessly communicate with anadditional wireless communicator. For example, the wireless communicatorWC is configured to wirelessly transmit to the additional wirelesscommunicator data sensed by the force sensor 262.

The electric power source PS is electrically connected to the electricalcomponent 260 and the wireless communicator WC to supply electricity tothe electrical component 260 and the wireless communicator WC. Forexample, the electric power source PS is configured to be provided inthe crank axle 16. The electric power source PS includes a battery.However, the electric power source PS can be provided in positions otherthan the inside of the crank axle 16 if needed and/or desired. Theelectric power source PS can include components other than the batteryif needed and/or desired.

The crank assembly 210 further comprises a cover member 264. The covermember 264 is configured to be attached to the axially inwardly facingcrank-surface 12B of the crank arm 12 so as to cover the electricalcomponent 260 in an assembled state of the crank assembly 210.

In the present embodiment, the cover member 264 is made of anon-metallic material. The cover member 264 is made of a resin materialsuch as synthetic resin.

However, the cover member 264 can be made of materials other than thenon-metallic material if needed and/or desired.

As seen in FIG. 21 , the crank assembly 210 includes an additional covermember 266. The additional cover member 266 is configured to be attachedto the crank arm 12. For example, the wireless communicator WC isprovided in the additional cover member 266. However, the wirelesscommunicator WC can be provided positions other than the inside of theadditional cover member 266 if needed and/or desired. The additionalcover member 266 can be configured to be attached to other parts of thecrank assembly 210 if needed and/or desired.

As seen in FIG. 22 , the first axial length L1 of the chain-drop controlsection 36 is longer than a minimum distance L6 defined between thechain-drop control protrusion 30 and the cover member 264 in the boreaxial direction D4. However, the first axial length L1 of the chain-dropcontrol section 36 can be shorter than or equal to the minimum distanceL6 if needed and/or desired.

In the present embodiment, the through bore 32 has the threaded portion32A and the non-threaded portion 32B. However, one of the threadedportion 32A and the non-threaded portion 32B can be omitted from thethrough bore 32 if needed and/or desired.

Third Embodiment

A crank assembly 310 in accordance with a third embodiment will bedescribed below referring to FIGS. 23 to 28 . The crank assembly 310 hasthe same structure and/or configuration as those of the crank assembly210 except for the chain-drop control protrusion 30. Thus, elementshaving substantially the same function as those in the first and secondembodiments will be numbered the same here and will not be describedand/or illustrated again in detail here for the sake of brevity.

As seen in FIG. 23 , the crank assembly 310 for the human poweredvehicle 2 comprises the crank arm 12 and the front sprocket unit 14. Thecrank assembly 310 comprises the crank axle 16.

As seen in FIG. 24 , the crank assembly 310 for the human poweredvehicle 2 comprises at least one chain-drop control member 330. In thepresent embodiment, the crank assembly 310 comprises a single chain-dropcontrol member 330. However, the crank assembly 310 comprises aplurality of chain-drop control members 330 if needed and/or desired.

As seen in FIG. 25 , the at least one chain-drop control member 330 isconfigured to inhibit the drive chain 4 from getting into the space SPprovided radially inwardly from the at least one chain-drop controlmember 330 and between the crank arm 12 and the front sprocket unit 14in the axial direction D2.

The at least one chain-drop control member 330 is configured to beprovided to at least one of the axially inwardly facing crank-surface12B of the crank arm 12 and the axially outwardly facingsprocket-surface 14A of the front sprocket unit 14. The chain-dropcontrol member 330 is configured to be provided to the axially outwardlyfacing sprocket-surface 14A among the axially inwardly facingcrank-surface 12B and the axially outwardly facing sprocket-surface 14A.However, the at least one chain-drop control member 330 can beconfigured to be provided to only the axially inwardly facingcrank-surface 12B or both of the axially inwardly facing crank-surface12B and the axially outwardly facing sprocket-surface 14A if neededand/or desired.

As seen in FIG. 26 , the at least one chain-drop control member 330 hasa proximal end 332 and a free distal end 334. The free distal end 334 isdisposed radially outwardly from the proximal end 332 with respect tothe rotational center axis A1. The free distal end 334 is disposedradially outwardly from the plurality of sprocket teeth 18B.

The proximal end 332 is attached to the at least one of the axiallyinwardly facing crank-surface 12B of the crank arm 12 and the axiallyoutwardly facing sprocket-surface 14A of the front sprocket unit 14. Inthe present embodiment, the proximal end 332 is attached to the axiallyoutwardly facing sprocket-surface 14A among the axially inwardly facingcrank-surface 12B and the axially outwardly facing sprocket-surface 14A.However, the proximal end 332 can be attached to only the axiallyinwardly facing crank-surface 12B or both of the axially inwardly facingcrank-surface 12B and the axially outwardly facing sprocket-surface 14Aif needed and/or desired.

As seen in FIG. 27 , the crank arm 12 has a maximum circumferentialcrank-width W1 in the circumferential direction D3 with respect to therotational center axis A1. The maximum circumferential crank-width W1 isdefined in the circumferential direction D3. In the present embodiment,the plurality of coupling parts 22 defines the maximum circumferentialcrank-width W1. However, other parts of the crank arm 12 can define themaximum circumferential crank-width W1 if needed and/or desired.

As seen in FIG. 28 , the at least one chain-drop control member 330 hasa maximum circumferential member-width W2 in the circumferentialdirection D3. As seen in FIGS. 27 and 28 , the maximum circumferentialmember-width W2 is equal to or smaller than the maximum circumferentialcrank-width W1. In the present embodiment, the maximum circumferentialmember-width W2 is smaller than the maximum circumferential crank-widthW1. However, the maximum circumferential member-width W2 can be largerthan or equal to the maximum circumferential crank-width W1 if neededand/or desired.

As seen in FIG. 28 , the plurality of sprocket teeth 18B each has acircumferential tooth-width W3 defined between adjacent tooth-bottomcenter-points TB in the circumferential direction D3. The sprocket tooth18B includes tooth-bottom center-points TB and is provided between thetooth-bottom center-points TB in the circumferential direction D3. Themaximum circumferential member-width W2 is equal to or larger than thecircumferential tooth-width W3. The maximum circumferential member-widthW2 is equal to or larger than double of the circumferential tooth-widthW3.

In the present embodiment, the maximum circumferential member-width W2is larger than the circumferential tooth-width W3. The maximumcircumferential member-width W2 is larger than double of thecircumferential tooth-width W3. However, the maximum circumferentialmember-width W2 can be smaller than or equal to the circumferentialtooth-width W3 if needed and/or desired. The maximum circumferentialmember-width W2 can be smaller than or equal to double of thecircumferential tooth-width W3 if needed and/or desired.

The proximal end 332 of the at least one chain-drop control member 330has a maximum circumferential proximal-width W4 in the circumferentialdirection D3. The maximum circumferential proximal-width W4 is definedin the circumferential direction D3. The maximum circumferentialproximal-width W4 is equal to or larger than the circumferentialtooth-width W3. In the present embodiment, the maximum circumferentialproximal-width W4 is larger than the circumferential tooth-width W3.However, the maximum circumferential proximal-width W4 can be smallerthan or equal to the circumferential tooth-width W3 if needed and/ordesired.

The free distal end 334 of the at least one chain-drop control member330 has a maximum circumferential distal-width W5 in the circumferentialdirection D3. The maximum circumferential distal-width W5 is defined inthe circumferential direction D3. The maximum circumferentialdistal-width W5 is equal to or larger than the circumferentialtooth-width W3. In the present embodiment, the maximum circumferentialdistal-width W5 is larger than the circumferential tooth-width W3.However, the maximum circumferential distal-width W5 can be smaller thanor equal to the circumferential tooth-width W3 if needed and/or desired.

As seen in FIG. 29 , the proximal end 332 is attached to the at leastone of the axially inwardly facing crank-surface 12B of the crank arm 12and the axially outwardly facing sprocket-surface 14A of the frontsprocket unit 14 at a plurality of points 332P. In the presentembodiment, the proximal end 332 is attached to the axially outwardlyfacing sprocket-surface 14A among the axially inwardly facingcrank-surface 12B and the axially outwardly facing sprocket-surface 14Aat the plurality of points 332P. However, the proximal end 332 can beattached to only the axially inwardly facing crank-surface 12B or bothof the axially inwardly facing crank-surface 12B and the axiallyoutwardly facing sprocket-surface 14A at the plurality of points 332P ifneeded and/or desired.

The chain-drop control member 330 includes a plurality of attachmentparts 335. The plurality of attachment parts 335 defines the pluralityof points 332P. The plurality of attachment parts 335 is spaced apartfrom each other in the circumferential direction D3. The plurality ofattachment parts 335 extends from the proximal end 332. The attachmentpart 335 is at least partially provided in the attachment hole 40 of thefront sprocket unit 14. In the present embodiment, the attachment part335 is partially provided in the attachment hole 40 of the frontsprocket unit 14. However, the attachment part 335 can be entirelyprovided in the attachment hole 40 of the front sprocket unit 14 ifneeded and/or desired.

The attachment part 335 includes a first attachment part 335A, a secondattachment part 335B, and a hole 335C. The first attachment part 335A isprovided in the attachment hole 40. The second attachment part 335B isprovided outside the attachment hole 40. The hole 335C has a center axisA3. The point 332P is defined on the center axis A3. The firstattachment part 335A has an annular shape. The second attachment part335B has an annular shape. The second attachment part 335B has an outerdiameter larger than an outer diameter of the first attachment part335A. For example, the second attachment part 335B is formed by beingswaged. However, the second attachment part 335B can be formed by othermethods. The second attachment part 335B can be omitted from theattachment part 335 e.g. if the attachment part 335 is coupled to theattachment hole 40 by an adhesive agent or in a press-fitting manner.

In the present embodiment, the free distal end 334 is integrallyprovided with the proximal end 332 as a one-piece unitary member. Theattachment part 335 is integrally provided with the proximal end 332 asa one-piece unitary member. However, the free distal end 334 can be aseparate member from the proximal end 332 if needed and/or desired. Atleast one of the attachment parts 335 can be a separate member from theproximal end 332 if needed and/or desired.

In the present embodiment, a total number of the points 332P is three. Atotal number of the attachment parts 335 is three. However, the totalnumber of the points 332P can be greater than or equal to two if neededand/or desired. The total number of the attachment parts 335 can begreater than or equal to two if needed and/or desired.

Modifications

In the first embodiment, as seen in FIG. 7 , the at least one chain-dropcontrol protrusion 30 is configured to be provided to the front sprocketunit 14 among the crank arm 12 and the front sprocket unit 14. The atleast one chain-drop control protrusion 30 is configured to be providedto the axially outwardly facing sprocket-surface 14A among the axiallyinwardly facing crank-surface 12B and the axially outwardly facingsprocket-surface 14A. As seen in FIGS. 30 and 31 , however, the at leastone chain-drop control protrusion 30 can be configured to be provided toonly the crank arm 12 or both of the crank arm 12 and the front sprocketunit 14 if needed and/or desired. The at least one chain-drop controlprotrusion 30 can be configured to be provided to the axially inwardlyfacing crank-surface 12B of the crank arm 12 or both of the axiallyinwardly facing crank-surface 12B of the crank arm 12 and the axiallyoutwardly facing sprocket-surface 14A of the front sprocket unit 14 ifneeded and/or desired. The same can be applied to the crank assembly 210in accordance with the second embodiment.

In the first and second embodiments and the modifications thereof, eachchain-drop control protrusion of the plurality of chain-drop controlprotrusions 30 has the same structure as each other. However, at leastone chain-drop control protrusion of the plurality of chain-drop controlprotrusions 30 can have a structure different from a structure ofanother chain-drop control protrusion of the plurality of chain-dropcontrol protrusions 30 if needed and/or desired.

In the first embodiment and the modifications thereof, each additionalchain-drop control protrusion of the plurality of additional chain-dropcontrol protrusions 50 has the same structure as each other. However, atleast one additional chain-drop control protrusion of the plurality ofadditional chain-drop control protrusions 50 can have a structuredifferent from a structure of another additional chain-drop controlprotrusion of the plurality of additional chain-drop control protrusions50 if needed and/or desired.

In the third embodiment, as seen in FIG. 26 , the at least onechain-drop control member 330 is configured to be provided to the frontsprocket unit 14 among the crank arm 12 and the front sprocket unit 14.The at least one chain-drop control member 330 is configured to beprovided to the axially outwardly facing sprocket-surface 14A among theaxially inwardly facing crank-surface 12B and the axially outwardlyfacing sprocket-surface 14A. As seen in FIGS. 32 and 33 , however, theat least one chain-drop control member 330 can be configured to beprovided to only the crank arm 12 or both of the crank arm 12 and thefront sprocket unit 14 if needed and/or desired. The at least onechain-drop control member 330 can be configured to be provided to theaxially inwardly facing crank-surface 12B of the crank arm 12 or both ofthe axially inwardly facing crank-surface 12B of the crank arm 12 andthe axially outwardly facing sprocket-surface 14A of the front sprocketunit 14 if needed and/or desired.

In the modification illustrated in FIG. 33 , each chain-drop controlmember of the plurality of chain-drop control members 330 has differentstructures from each other. However, at least one chain-drop controlmember of the plurality of chain-drop control members 330 can have thesame structure as a structure of another chain-drop control member ofthe plurality of chain-drop control members 330 if needed and/ordesired.

The first to third embodiments and the modifications thereof can becombined with each other if needed and/or desired. For example, thecrank assembly 10 can comprise at least one chain-drop controlprojection 30 and at least one chain-drop control member 50.

In the present application, the term “comprising” and its derivatives,as used herein, are intended to be open ended terms that specify thepresence of the stated features, elements, components, groups, integers,and/or steps, but do not exclude the presence of other unstatedfeatures, elements, components, groups, integers and/or steps. Thisconcept also applies to words of similar meaning, for example, the terms“have,” “include” and their derivatives.

The terms “member,” “section,” “portion,” “part,” “element,” “body” and“structure” when used in the singular can have the dual meaning of asingle part or a plurality of parts.

The ordinal numbers such as “first” and “second” recited in the presentapplication are merely identifiers, but do not have any other meanings,for example, a particular order and the like. Moreover, for example, theterm “first element” itself does not imply an existence of “secondelement,” and the term “second element” itself does not imply anexistence of “first element.”

The term “pair of,” as used herein, can encompass the configuration inwhich the pair of elements have different shapes or structures from eachother in addition to the configuration in which the pair of elementshave the same shapes or structures as each other.

The terms “a” (or “an”), “one or more” and “at least one” can be usedinterchangeably herein.

The phrase “at least one of” as used in this disclosure means “one ormore” of a desired choice. For one example, the phrase “at least one of”as used in this disclosure means “only one single choice” or “both oftwo choices” if the number of its choices is two. For other example, thephrase “at least one of” as used in this disclosure means “only onesingle choice” or “any combination of equal to or more than two choices”if the number of its choices is equal to or more than three. Forinstance, the phrase “at least one of A and B” encompasses (1) A alone,(2), B alone, and (3) both A and B. The phrase “at least one of A, B,and C” encompasses (1) A alone, (2), B alone, (3) C alone, (4) both Aand B, (5) both B and C, (6) both A and C, and (7) all A, B, and C. Inother words, the phrase “at least one of A and B” does not mean “atleast one of A and at least one of B” in this disclosure.

Finally, terms of degree such as “substantially,” “about” and“approximately” as used herein mean a reasonable amount of deviation ofthe modified term such that the end result is not significantly changed.All of numerical values described in the present application can beconstrued as including the terms such as “substantially,” “about” and“approximately.”

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A crank assembly for a human-powered vehicle, the crank assemblycomprising: a crank arm having an axially outwardly facing crank-surfaceand an axially inwardly facing crank-surface provided on a reverse sideof the axially outwardly facing crank-surface in an axial direction withrespect to a rotational center axis of the crank assembly, the axiallyinwardly facing crank-surface being configured to face toward an axialcenter plane of the human powered vehicle in the axial direction in amounted state where the crank assembly is mounted to the human poweredvehicle; a front sprocket unit having an axially outwardly facingsprocket-surface and an axially inwardly facing sprocket-surfaceprovided on a reverse side of the axially outwardly facingsprocket-surface in the axial direction, the axially inwardly facingsprocket-surface being configured to face toward the axial center planeof the human powered vehicle in the axial direction in the mountedstate, the front sprocket unit including: a sprocket body; and aplurality of sprocket teeth extending radially outwardly from thesprocket body in a radial direction with respect to the rotationalcenter axis; and at least one chain-drop control protrusion configuredto inhibit a drive chain from getting into a space provided radiallyinwardly from the at least one control protrusion and between the crankarm and the front sprocket unit in the axial direction, the at least onechain-drop control protrusion being configured to be provided to atleast one of the axially inwardly facing crank-surface of the crank armand the axially outwardly facing sprocket-surface of the front sprocketunit, the at least one chain-drop control protrusion having a throughbore, an entirety of the at least one chain-drop control protrusion isdisposed radially inwardly from an outermost tip of the plurality ofsprocket teeth.
 2. A crank assembly for a human-powered vehicle, thecrank assembly comprising: a crank arm having an axially outwardlyfacing crank-surface and an axially inwardly facing crank-surfaceprovided on a reverse side of the axially outwardly facing crank-surfacein an axial direction with respect to a rotational center axis of thecrank assembly, the axially inwardly facing crank-surface beingconfigured to face toward an axial center plane of the human poweredvehicle in the axial direction in a mounted state where the crankassembly is mounted to the human powered vehicle; a front sprocket unithaving an axially outwardly facing sprocket-surface and an axiallyinwardly facing sprocket-surface provided on a reverse side of theaxially outwardly facing sprocket-surface in the axial direction, theaxially inwardly facing sprocket-surface being configured to face towardthe axial center plane of the human powered vehicle in the axialdirection in the mounted state, the front sprocket unit including: asprocket body; and a plurality of sprocket teeth extending radiallyoutwardly from the sprocket body in a radial direction with respect tothe rotational center axis; and at least one chain-drop controlprotrusion configured to inhibit a drive chain from getting into a spaceprovided radially inwardly from the at least one control protrusion andbetween the crank arm and the front sprocket unit in the axialdirection, the at least one chain-drop control protrusion beingconfigured to be provided to at least one of the axially inwardly facingcrank-surface of the crank arm and the axially outwardly facingsprocket-surface of the front sprocket unit, the at least one chain-dropcontrol protrusion having a through bore, wherein the at least onechain-drop control protrusion has a free end and an attachment endconfigured to be coupled to the at least one of the axially inwardlyfacing crank-surface of the crank arm and the axially outwardly facingsprocket-surface of the front sprocket unit; and the through bore has abore center-axis extending from one of the free end and the attachmentend to the other of the free end and the attachment end.
 3. The crankassembly according to claim 2, wherein the at least one chain-dropcontrol protrusion has a chain-drop control section and an attachmentsection adjacent to the chain-drop control section in a bore axialdirection with respect to the bore center-axis, the chain-drop controlsection includes the free end, and the attachment section includes theattachment end.
 4. The crank assembly according to claim 3, wherein thechain-drop control section has a first maximum diameter with respect tothe bore center-axis, the attachment section has a second maximumdiameter with respect to the bore center-axis, and the first maximumdiameter is larger than the second maximum diameter.
 5. The crankassembly according to claim 3, wherein the chain-drop control sectionhas a first axial length with respect to the bore center-axis, theattachment section has a second axial length with respect to the borecenter-axis, and the first axial length is larger than the second axiallength.
 6. The crank assembly according to claim 3, wherein thechain-drop control section has a radially outermost surface with respectto the bore center-axis and a chamfered portion, the free end has anaxial free-end surface with respect to the bore center-axis, and thechamfered portion is provided between the radially outermost surface andthe axial free-end surface.
 7. The crank assembly according to claim 6,wherein the chamfered portion has a curvature.
 8. The crank assemblyaccording to claim 3, wherein the through bore has a threaded portionprovided at least in the chain-drop control section of the at least onechain-drop control protrusion.
 9. The crank assembly according to claim8, further comprising: an additional chain-drop control protrusionconfigured to threadedly engage with the threaded portion of the throughbore.
 10. The crank assembly according to claim 3, wherein the throughbore has a large diameter bore and a small diameter bore connected tothe large diameter bore, the large diameter bore extends from the freeend in a bore axial direction with respect to the bore center-axis, andthe small diameter bore extends from the attachment end in the boreaxial direction.
 11. The crank assembly according to claim 10, whereinthe large diameter bore and the small diameter bore are connected toeach other at a connecting point, and the threaded portion extends fromthe connecting point along the bore axial direction in the smalldiameter bore.
 12. The crank assembly according to claim 11, wherein theconnecting point is located in the chain-drop control section.
 13. Thecrank assembly according to claim 3, wherein the attachment section hasa non-circular cross-sectional shape.
 14. The crank assembly accordingto claim 8, wherein the at least one chain-drop control protrusion has achain-drop control section and an attachment section adjacent to thechain-drop control section in a bore axial direction with respect to thebore center-axis, the through bore has a non-threaded portion providedin the attachment section and adjacent to the threaded portion, and thenon-threaded portion has a non-threaded internal diameter that is equalto an internal minor diameter of the threaded portion.
 15. The crankassembly according to claim 1, further comprising: an electricalcomponent provided to the crank arm at a location radially inwardly fromthe at least one chain-drop control protrusion.
 16. The crank assemblyaccording to claim 15, wherein the electrical component includes a forcesensor.
 17. The crank assembly according to claim 15, furthercomprising: a cover member configured to be attached to the axiallyinwardly facing crank-surface of the crank arm so as to cover theelectrical component in an assembled state of the crank assembly. 18.The crank assembly according to claim 17, wherein the cover member ismade of a non-metallic material.
 19. A crank assembly for ahuman-powered vehicle, the crank assembly comprising: a crank arm havingan axially outwardly facing crank-surface and an axially inwardly facingcrank-surface provided on a reverse side of the axially outwardly facingcrank-surface in an axial direction with respect to a rotational centeraxis of the crank assembly, the axially inwardly facing crank-surfacebeing configured to face toward an axial center plane of the humanpowered vehicle in the axial direction in a mounted state where thecrank assembly is mounted to the human powered vehicle; a front sprocketunit having an axially outwardly facing sprocket-surface and an axiallyinwardly facing sprocket-surface provided on a reverse side of theaxially outwardly facing sprocket-surface in the axial direction, theaxially inwardly facing sprocket-surface being configured to face towardthe axial center plane of the human powered vehicle in the axialdirection in the mounted state, the front sprocket unit including: asprocket body; and a plurality of sprocket teeth extending radiallyoutwardly from the sprocket body in a radial direction with respect tothe rotational center axis; and at least one chain-drop controlprotrusion configured to inhibit a drive chain from getting into a spaceprovided radially inwardly from the at least one control protrusion andbetween the crank arm and the front sprocket unit in the axialdirection, the at least one chain-drop control protrusion beingconfigured to be provided to at least one of the axially inwardly facingcrank-surface of the crank arm and the axially outwardly facingsprocket-surface of the front sprocket unit, the at least one chain-dropcontrol protrusion having a through bore, wherein the at least onechain-drop control protrusion includes a plurality of chain-drop controlprotrusions spaced apart from each other in a circumferential directionwith respect to the rotational center axis.
 20. The crank assemblyaccording to claim 1, wherein the at least one chain-drop controlprotrusion is disposed radially inwardly from the plurality of sprocketteeth.
 21. A crank assembly for a human-powered vehicle, the crankassembly comprising: a crank arm having an axially outwardly facingcrank-surface and an axially inwardly facing crank-surface provided on areverse side of the axially outwardly facing crank-surface in an axialdirection with respect to a rotational center axis of the crankassembly, the axially inwardly facing crank-surface being configured toface toward an axial center plane of the human powered vehicle in theaxial direction in a mounted state where the crank assembly is mountedto the human powered vehicle; a front sprocket unit having an axiallyoutwardly facing sprocket-surface and an axially inwardly facingsprocket-surface provided on a reverse side of the axially outwardlyfacing sprocket-surface in the axial direction, the axially inwardlyfacing sprocket-surface being configured to face toward the axial centerplane of the human powered vehicle in the axial direction in the mountedstate, the front sprocket unit including: a sprocket body; and aplurality of sprocket teeth extending radially outwardly from thesprocket body in a radial direction with respect to the rotationalcenter axis; at least one chain-drop control protrusion configured toinhibit a drive chain from getting into a space provided radiallyinwardly from the at least one control protrusion and between the crankarm and the front sprocket unit in the axial direction, the at least onechain-drop control protrusion being configured to be provided to atleast one of the axially inwardly facing crank-surface of the crank armand the axially outwardly facing sprocket-surface of the front sprocketunit; and an electrical component provided to the axially inwardlyfacing crank-surface of the crank arm at a location radially inwardlyfrom the at least one chain-drop control protrusion and between thecrank arm and the front sprocket in the axial direction.
 22. The crankassembly according to claim 21, wherein the at least one chain-dropcontrol protrusion has a through bore.